Ground-water contribution from the Silurian/Devonian carbonate aquifer to the Mad River Valley, southwestern Ohio : R. A. Sheets & W. P. Yost, Ohio Journal of Science, 94(5), 1994, pp 138–146

Abstract

The U.S. Geological Survey Regional Aquifer-System Analysis is examining the Silurian and Devonian carbonate aquifer and overlying glacial deposits of western Ohio and eastern Indiana in terms of the hydrogeologic framework, ground-water-flow system and water chemistry, and response to withdrawals and development. This paper describes the hydrogeology of an area in southwestern Ohio that contains the Mad River Valley, an outwash valley that is incised through the relatively permeable Silurian bedrock into the relatively Ordovician bedrock at the southern boundary of Silurian rocks. Ground-water-flow patterns based on a synoptic water-level survey of 80 bedrock wells in the Silurian and Devonian carbonate aquifer indicate that flow is toward the valley. A ground-water basin was delineated from the potentiometricsurface map and used in conjunction with a low-flow gain-loss study to derive a generalized ground-water/ surface-water budget for the area. Results of this budget indicate that ground-water recharge rates through the ground moraine to the carbonate aquifer range from 4 to 6 in/yr (10-15 cm/yr) and that approximately 60 to 80% of the base flow in the Mad River may ultimately consist of ground water derived from the Silurian and Devonian carbonate aquifer. Previous studies of surfaceand ground-water chemistry in the area also support the conclusion that the Mad River Valley functions as a discharge area for the surrounding carbonate aquifer. Results of this study can be useful in characterizing ground-water flow and recharge rates for the Silurian and Devonian carbonate and valley aquifers along the southern boundary of this extensive regional aquifer system. OHIO J. SCI. 94 (5): 138-146, 1994 INTRODUCTION In 1988, the U.S. Geological Survey's Regional AquiferSystem Analysis (RASA) program began an investigation of the hydrogeologic framework, the present ground-water-flow system and water chemistry, and effects of ground-water development in the Midwestern Basin and Arches Region (Fig. 1). This RASA investigation has focused primarily on the Silurian and Devonian carbonates and surficial unconsolidated deposits of western Ohio and eastern Indiana (Bugliosi 1990). A major objective of this RASA is characterization of the aquifer system, in terms of regional ground-water-flow patterns. A system of river valleys filled with various lacustrine, alluvial, and glacial deposits is present throughout the Silurian and Devonian carbonate aquifer system. These valleys were formed predominantly as a result of several Pleistocene continental glaciations. As the ice retreated northward, sediment-laden rivers incised the bedrock of western Ohio and eastern Indiana, creating the valleys and later depositing valley-fill material. The hydrologic characteristics of these valleys vary with the type of materials deposited in them and the depth of incision into the bedrock. In some valleys, unconsolidated deposits yield more ground water than the bedrock that they incise; in other valleys, usable ground-water resources are negligible. The hydrologic interaction of these valleys with the ground-water-flow regime of the permeable bedrock is important to the understanding of boundary conditions for the regional ground-water analysis. 'Manuscript received 8 April 1994 and in revised form 12 September 1994 (#94-07). Previous Investigations Orton (1874) and Leverett (1897) were probably among the first to describe the water-bearing potential of bedrock and unconsolidated deposits of southwestern Ohio. Fuller and Clapp (1912) wrote an overview of the area's water resources, which includes a county-bycounty description of the physiography, springs, wells, and the water-bearing potential of lithologic units. The large water-bearing potential of the river valleys in this part of Ohio has led many authors to publish waterresource information for these valleys (e.g., Norris and Spieker 1966, Norris and Eagon 1971). In contrast, few publications describe the ground-water resources of the Ordovician shale and limestone subcrops in this area, probably because of the scarcity of potable ground water, which would limit the amount of subsurface data available from well drillers. In fact, most authors refer to the Ordovician bedrock as impermeable or impervious to ground-water flow (Orton 1874; Fuller and Clapp 1912; Harker and Bernhagen 1943; and Norris et al. 1947, 1949, 1952). Works that describe the Silurian and Devonian carbonate aquifer system in this area are more numerous than those that describe the Ordovician bedrock, but are less numerous than those that describe ground-water resources of the valleys. Purpose and Scope The purpose of this paper is to describe the hydrogeology of the Mad River Valley aquifer system in southwestern Ohio and its hydrologic relation to the surrounding Silurian and Devonian carbonate aquifer that it incises. Ground-water flow based on measured water levels in the Silurian and Devonian carbonate aquifer, stream-discharge measurements of the Mad River OHIO JOURNAL OF SCIENCE R. A. SHEETS AND W. P. YOST 139